Acid sulfate soils are natural sediments that contain iron sulfides. They are common along the NSW coast. When disturbed or exposed to air these soils can release acid, damaging built structures and harming or killing animals and plants.
The map classifies coastal land below 10 m elevation (AHD) into various risk classes depending on the probability of the acid sulfate soil hazard and the depth at which acid sulfate materials are likely to be encountered. The risk classes are:
| Class | Definition |
| Hm | High probability, bottom sediments |
| H0 | High probability at/near ground surface |
| H1 | High probability <1 m below ground surface |
| H2 | High probability 1–3 m below ground surface |
| H4 | High probability >3 m below ground surface |
| Lm | Low probability, bottom sediments |
| L0 | Low probability, at/near ground surface |
| L1 | Low probability, <1 m below ground surface |
| L2 | Low probability, 1–3 m below ground surface |
| L4 | Low probability, >3 m below ground surface |
| N | No known occurrence |
| NB | No known occurrence, beach |
| X0 | Disturbed terrain, elevation <1 m AHD |
| X1 | Disturbed terrain, elevation 1-2 m AHD |
| X2 | Disturbed terrain, elevation 2-4 m AHD |
| X4 | Disturbed terrain, elevation >4 m AHD |
For more information about acid sulfate soils, go to environment.nsw.gov.au/topics/land-and-soil/soil-degradation/acid-sulfate-soils. More maps and information about acid sulfate soils in NSW are available on eSPADE at espade.environment.nsw.gov.au
